Due to the demand of healthcare, nondestructive medical detection methods have become popular gradually. Among various nondestructive detection methods, the computerized tomography (CT) technology has been applied extensively. In a computerized tomography equipment, an essential part involves sensors.
A basic structure of a sensor is shown in FIG. 1. The sensor 12 includes a plurality of gate lines 15, a plurality of data lines 16 and a plurality of sensing units each including a photodiode 13 and a field effect transistor (FET) 14. A gate of the field effect transistor 14 is connected with a corresponding gate line 15 of the sensor 12, a source of the field effect transistor 14 is connected with a corresponding data line 16 of the sensor 12, and the photodiode 13 is connected with a drain of the field effect transistor 14. One end of each of these data lines 16 is connected to a data reading circuit 18 via a connection pin 17.
The operation principle of the above-mentioned sensor is as follows: The sensor 12 applies a driving scan signal through the gate line 15 to control the on- or off-state of the field effect transistor 14 of each sensing unit. When the field effect transistor 14 is turned on, photocurrent signal generated by the photodiode 13 successively passes the data line 16 and the data reading circuit 18 connected with the field effect transistor 14 to be output, and photocurrent signal collection function is implemented by controlling signal sequence on the gate line 15 and the data line 16, that is, the collection of photocurrent signal generated by the photodiode 13 is controlled by controlling the on off state of the FET 14.
At present, sensors generally adopt thin film transistor (TFT) slab structure which has a plurality of layers in the section. For example, a sensing unit includes a substrate, a gate layer, a gate insulating layer, an active layer, a source-and-drain layer, a passivation layer, a PI junction and a transparent window layer of a PIN photoelectric sensor, and a biasing line layer and a light barrier layer. Of course, different sensors have more or less different pattern layers in section due to different structures.
In the above existing sensor structures, the coverage of the photodiode is relatively limited, which results in a small light receiving area of the sensor, a low absorption and utilization ratio of light, a high dissipation of energy and incapability of further improving imaging quality.